This application claims the benefit of a Japanese Patent Application No. 2000-285761 filed Sep. 20, 2000, in the Japanese Patent Office, the disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to data read methods and storage apparatuses, and more particularly to a data read method which remedies low-quality read data and to a storage apparatus which employs such a data read method.
Recently, due to the increasing storage capacities of disks used in storage apparatuses such as magnetic disk units and optical disk units, there are demands to maintain high quality of read data read from the disk.
2. Description of the Related Art
Conventionally, the high quality of the read data is achieved by carrying out processes such as a retry process and an error detecting and correcting process. In the case of the optical disk unit, for example, the retry process improves the remedy efficiency of the read data by varying various retry parameters such as focus offset. In addition, the error detecting and correcting process improves the quality of the read data by using an error correction code (ECC). Accordingly, it is possible to improve the quality of the read data by carrying out the retry process and the error detecting and correcting process.
However, in the case of the optical disk, for example, a land recording system is employed to record data on lands which are separated by grooves. Recently, a so-called land-groove recording system has been proposed to record the data on both the land and the groove which are alternately provided in a radial direction of the optical disk. In the optical disk which employs this land-groove recording system, a distance between two adjacent tracks is extremely short, and a crosstalk is easily generated from the adjacent tracks to thereby deteriorate the quality of the read data.
Therefore, in an environment where the crosstalk is easily generated from the adjacent tracks of the recording medium due to the high data recording density on the recording medium such as the disk, the quality of the read data is poor, and there is a problem in that it is difficult to remedy the read data even when the conventional processes such as the retry process and the error detecting and correcting process are carried out.
The above described problem is not peculiar to the optical disk, and similar problems also occur in other recording media such as the magnetic disk due to the effects of the crosstalk caused by narrowing of the track pitch.
Accordingly, it is a general object of the present invention to provide a novel and useful data read method and storage apparatus, in which the problem described above is eliminated.
Another and more specific object of the present invention is to provide a data read method and a storage medium, which remedy read data, so that high-quality read data can be obtained even when the quality of the actual read data is poor.
Still another object of the present invention is to provide a data read method comprising the steps of (a) reading identical data from one region on a recording medium a plurality of times, (b) comparing the data read the plurality of times in units of one or a plurality of bits to obtain comparison results, and generating read data made up of data values having a highest frequency for each unit based on the comparison results, and (c) carrying out an error detecting and correcting process with respect to the read data. According to the data read method of the present invention, it is possible to remedy the read data, so that high-quality read data can be obtained even when the quality of the actual read data is poor.
A further object of the present invention is to provide a storage apparatus comprising reading means for reading identical data from one region on a recording medium a plurality of times, generating means for comparing the data read the plurality of times in units of one or a plurality of bits to obtain comparison results, and generating read data made up of data values having a highest frequency for each unit based on the comparison results, and correcting means for carrying out an error detecting and correcting process with respect to the read data. According to the storage apparatus of the present invention, it is possible to remedy the read data, so that high-quality read data can be obtained even when the quality of the actual read data is poor.
Another object of the present invention is to provide a storage apparatus comprising a reading section reading identical data from one region on a recording medium a plurality of times, a generating section comparing the data read the plurality of times in units of one or a plurality of bits to obtain comparison results, and generating read data made up of data values having a highest frequency for each unit based on the comparison results, and an error correcting section carrying out an error detecting and correcting process with respect to the read data. According to the storage apparatus of the present invention, it is possible to remedy the read data, so that high-quality read data can be obtained even when the quality of the actual read data is poor.
The present invention is particularly effective with respect to a state where a random error, that is, a carrier-to-noise ratio (CNR) is low, and a noise component relatively appears large.
In addition, it is possible to increase the possibility of hitting a correct data, by carrying out the read process a plurality of times and employing the value having the highest appearing frequency.
Furthermore, even in a state where the CNR deteriorates not only due to a crosstalk from an adjacent track on the recording medium but also due to dust particles or the like adhered on the surface of the recording medium, it is possible to improve the apparent CNR by carrying out the read process a plurality of times in case of a random error and employing the value having the highest appearing frequency.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.